Approximately half the population have experienced a lucid dream. Yet, it is not well understood how an individual realises they are dreaming (i.e. lucid insight). A few studies suggest it can be triggered by a nightmare, or by the identification of inconsistencies/dream-like qualities/peculiarities. The present study aimed to produce a detailed typology of lucidity triggers to inform consideration of the nature of associated thought processes. 91 lucid dreamers were identified in an undergraduate sample of 148. Lucid dreamers were asked to describe what it was, if anything, that had made them realise they were dreaming. Thematic analysis of responses extracted evidence of four overarching triggers consistent with previous research: identification of an abnormality, identification of a dream-like quality, an emotionally-arousing dream event, and miscellaneous. It was uniquely identified that 'abnormalities' within the dream were those inconsistent with waking knowledge rather than with the accompanying dream content. Novel triggers were identified that were classifiable as subthemes under the previously-identified triggers, and triggers co-occurred in a third of cases. Novel triggers included 'déjà rêvé', the feeling that one has dreamt the experience before, as well as 'self-comfort/denial' involving an emotionally-driven denial of the reality of a distressing dream. Nightmare-induced lucidity appeared to arise via qualitatively diverse paths: via self-comfort/denial and/or via the identification of abnormalities/dream-like qualities. The nature of the triggers indicates that higher-order cognition can precede, and promote, lucid insight. This sheds light on a key theoretical issue of whether lucid insight is a prerequisite for the re-emergence of higher-order cognition.